Expandable tubulars are increasingly used in oil and gas production wells and may comprise slots or other perforations which are widened as a result of the expansion or may have a continuous ‘un-slotted’ wall which is circumferentially stretched by an expansion device such as an expansion cone and/or a set of rollers.
Expandable tubulars are generally joined by mechanical connectors since welding may create at least some strengthening and/or weakening of the pipe wall in the region of the weld, and strengthening will hamper or even disrupt the expansion process whereas weakening will result in a tube which will easily collapse, buckle and/or burst in the welding zone.
In addition, here it is required to weld slotted liners there are particular problems to overcome. In the first instance slotted expandable tubulars are difficult to seal completely to allow flushing with non-oxidising or reducing gases or gas mixtures and removal of air. In the second place welding the end of unprepared slotted liners will also cause the slots at the end of the tubular to be welded also. This impedes expansion and prevents proper functioning of the slotted expandable tubular.
It is known from International patent application WO 98/33619 to connect expandable tubulars by amorphous bonding and from International patent application WO 0230611 to connect expandable tubulars by laser welding. However, these connection techniques are time consuming and require a very precise positioning of the pipe ends relative to each other and machining the pipe ends into an extremely accurate flat shape. These technologies are not practical for use on for example a drilling rig, an offshore oil platform or pipe laying vessel.